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Cosmic string: The search continues

By Stephen Battersby

COSMIC string bears little relation to its humble domestic namesake. Forming lines of energy billions of light years long, it is narrower than a proton, and so dense that a piece 1 metre long weighs as much as an entire continent. Cosmic string is convulsed by ancient energies. It moves at almost the speed of light, shaking the fabric of space and time. It is not suitable for tying up small parcels.

In recent years, physicists have found that their theories are determined to spin out some kind of cosmic string. It also keeps cropping up in all sorts of experiments aimed at modelling the early universe. Although we have never seen it, many cosmologists are now convinced it is out there.

Our best theories of the early universe seem determined to include cosmic string

Cosmic string would be handy stuff&colon; stirring up magnetic fields, illuminating the early universe and firing out energetic particles (see “Useful stuff, string”). If we found a strand, it would tell us something about the fundamental nature of reality. We might discover that cosmic strings are giant cousins of the tiny “superstrings” thought to make up all matter. Or we might find we have unearthed a relic of the big bang, a place where the chaos of those earliest moments persists to this day.

It all hinges on the original theory of cosmic string being right. The idea dates back to 1976 when theoretical physicist Tom Kibble of Imperial College London suggested that string-like defects were formed in the aftermath of the big bang. As the hot young universe cooled down, …